Abstract
Arsenic (As) and lead (Pb) contamination in groundwater is a serious problem in countries that use groundwater as drinking water. In this study, composite beads, called SCM beads, synthesized using stone powder (SP), chitosan (Ch), and maghemite (Mag) with different weight ratios (1/1/0.1, 1/1/0.3, and 1/1/0.5 for SP/Ch/Mag) were prepared, characterized and used as adsorbents for the removal of As and Pb from artificially contaminated water samples. Adsorption isotherm experiments of As and Pb onto the beads were conducted and single-solute adsorption isotherm models such as the Langmuir, Freundlich, Dubinin–Radushkevich (DR), and dual mode (DM) models were fitted to the experimental data to analyze the adsorption characteristics. The maximum adsorption capacities of the SCM beads were 75.7 and 232.8 mmol/kg for As and Pb, respectively, which were 40 and 5.6 times higher than that of SP according to the Langmuir model analyses. However, the DM model had the highest determinant coefficient (R2) values for both As and Pb adsorption, indicating that the beads had heterogenous adsorption sites with different adsorption affinities. These magnetic beads could be utilized to treat contaminated groundwater.
Highlights
Groundwater contamination has become a serious environmental concern throughout the world
SCM composite beads were prepared with different mass ratios of 1/1/0.1, 1/1/0.3, and 1/1/0.5 of stone powder (SP)/chitosan/maghemite, respectively, for the adsorption of As and Pb
From the results of the model fitting, the beads had multiple adsorption sites with different affinities resulting from the inclusion of maghemite compared with SP and the dual mode (DM) model was the best model to describe these differences
Summary
Groundwater contamination has become a serious environmental concern throughout the world. In several countries such as Bangladesh, Vietnam, Pakistan, and China as well as the USA, Hungary, and Mexico, many people are exposed to high levels of arsenic (As) and/or lead (Pb) via the intake of contaminated groundwater [1,2,3,4,5]. Various technologies for As and Pb removal from contaminated water have been developed, including adsorption, ion exchange, pH control, and precipitation [7,8]. Adsorption is considered to be one of the more attractive technologies, and various adsorbents that are effective in As and Pb removal have been developed. For Pb removal, soils [20,21,22,23], zeolite [24], carbon aerogel [25], and metal oxides, such as iron oxides [26,27,28] and aluminum oxides [29], have been studied
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